Textile treatment compositions suitable for providing fabric softening and static control benefits during laundering are well-known in the art and have found wide-scale commercial application. Conventionally, rinse-added fabric softening compositions contain, as the active softening component, substantially water-insoluble cationic materials having two long alkyl chains. Typical of such materials are di-stearyl di-methyl ammonium chloride and imidazolinium compounds substituted with two stearyl groups. These materials are normally prepared in the form of a dispersion in water and it is generally not possible to prepare such aqueous dispersions with more than about 10% of cationic materials without encountering intractable problems of product viscosity and stability, especially after storage at elevated temperatures, such that the compositions are unpourable and have inadequate dispensing and dissolving characteristics in rinse water. This physical restriction on softener concentration naturally limits the level of softening performance achievable without using excessive amounts of product, and also adds substantially to the costs of distribution and packaging. Accordingly it would be highly desirable to have a method for preparing physically-acceptable textile treatment compositions containing much higher levels of water-insoluble cationic softener materials.
It would also be desirable to have a method for preparing fabric softeners which are storage-stable, and also which are biodegradable. However, materials which may be biodegradable are often difficult to formulate as stable liquid compositions.
It is an object of this invention to provide a novel method for manufacturing biodegradable fabric softener compositions. It is a further object to provide a method for manufacturing liquid fabric softening compositions, including concentrates, containing quaternized di-esters of di-isopropanol amines which exhibit improved stability and viscosity characteristics, even after prolonged storage. These and other objects are obtained by following the procedure described herein.
Cationic softener materials are normally supplied by the manufacturer in the form of a slurry containing about 70%-95% of active material in an organic liquid such as isopropanol, sometimes containing a minor amount of water (up to about 10%). Retail fabric softening compositions are then prepared by dispersion of the softener slurry in warm water under carefully controlled conditions. The physical form and dispersibility constraints of these industrial concentrates, however, are such as to preclude their direct use by the domestic consumer; indeed, they can pose severe processing problems even for the industrial supplier of retail fabric softening compositions.
The use of various quaternized ester amines as fabric softening agents is known in the art. See, for example, U.S. Pat. No. 4,339,391, Hoffmann, et al, issued July 13, 1982, for a series of quaternized ester-amines which function as fabric softeners. Various quaternized ester-amines are commercially available under the tradenames SYNPROLAM FS from ICI and REWOQUAT CR 3099 from REWO. However, neither the specific quaternized di-esters of di-isopropanol amines of the present invention, nor the desirable fabric softener/viscosity/stability/biodegradability properties of the fabric softening compositions manufactured in the manner disclosed herein appear to have been appreciated heretofore.
U.S. Pat. Nos. 4,426,299, issued Jan. 17, 1984, and 4,401,578, issued Aug. 30, 1983, Verbruggen, relate to paraffin, fatty acids and ester extenders for softener concentrates.
European Pat. No. 0,018,039, Clint, et al, issued Mar. 7, 1984, relates to hydrocarbons plus soluble cationic or nonionic surfactants in softener concentrates to improve viscosity and stability characteristics.
U.S. Pat. No. 4,454,049, MacGilp, et al, issued June 12, 1984, discloses concentrated liquid textile treatment compositions in the form of isotropic solutions comprising water-insoluble di-C.sub.16 -C.sub.24 optionally hydroxy-substituted alkyl, alkaryl or alkenyl cationic fabric softeners, at least about 70% of the fabric softener consisting of one or more components together having a melting completion temperature of less than about 20.degree. C., a water-insoluble nonionic extender, especially C.sub.10 -C.sub.40 hydrocarbons or esters of mono- or polyhydric alcohols with C.sub.8 -C.sub.24 fatty acids, and a water-miscible organic solvent. The concentrates have improved formulation stability and dispersibility, combined with excellent fabric softening characteristics.
U.S. Pat. No. 4,439,330, Ooms, issued Mar. 27, 1984, teaches concentrated softeners comprising ethoxylated amines.
U.S. Pat. No. 4,476,031, Ooms, issued Oct. 9, 1984, teaches ethoxylated amines or protonated derivatives thereof, in combination with ammonium, imadazolinium, and like materials. The use of alkoxylated amines, as a class, in softener compositions is known (see, for example, German Patent Applications Nos. 2,829,022, Jakobi and Schmadel, published Jan. 10, 1980, and 1,619,043, Mueller et al., published Oct. 30, 1969, and U.S. Pat. Nos. 4,076,632, Davis, issued Feb. 28, 1978, and 4,157,307, Jaeger and Davis, issued June 5, 1979).
U.S. Pat. No. 4,422,949, Ooms, issued Dec. 27, 1983, relates to softener concentrates based on ditallow dimethyl ammonium chloride (DTDMAC), glycerol monostearate and polycationics.
In United Kingdom Application No. 2,007,734A, Sherman et al., published May 23, 1979, fabric softener concentrates are disclosed which contain a mixture of a fatty quaternary ammonium salt having at least one C.sub.8 -C.sub.30 alkyl substituent and an oil or substantially water-insoluble compound having oily/fatty properties. The concentrates are said to be easily dispersed/emulsified in cold water to form fabric softening compositions.
Concentrated dispersions of softener material can be prepared as described in European Patent Application No 406 and United Kingdom Patent Specification No. 1,601,360, Goffinet, published Oct. 28, 1981, by incorporating certain nonionic adjunct softening materials therein.
As can be seen, the specific problem of preparing fabric softening compositions in concentrated form suitable for consumer use has been addressed in the art, but the various solutions have not been entirely satisfactory. It is generally known (for example, in U.S. Pat. No. 3,681,241, Rudy, issued Aug. 1, 1972,) that the presence of ionizable salts in softener compositions does help reduce viscosity, but this approach is ineffective in compositions containing more than about 12% of dispersed softener, inasmuch as the level of ionizable salts necessary to reduce viscosity to any substantial degree has a seriously detrimental effect on product stability.